Pulse position/width collaborative control for reducing EMI noise and ripple voltage in switching DC-DC converter

A novel method for “pulse position/width collaborative control” in a switching DC-DC converter-for reducing both electro-magnetic-interference (EMI) noise and output ripple voltage-is proposed. A switching DC-DC converter inherently produces large EMI noise because of its periodical switching-control operation. Pulse-position modulation (PPM) is one method for reducing EMI noise by spreading the switching control signal. As a trade-off, however, output ripple voltage increases because the variation of pulse density causes fluctuation of output voltage. The proposed control method reduces EMI noise by spreading pulse positions and compensates pulse-density variation by controlling pulse widths collaboratively. Unlike conventional PPM, the proposed control method reduces ripple voltage. Model-based simulations and experimental measurements confirmed the advantage of the proposed control method; namely, EMI noise is reduced by 12 dB, while output ripple voltage is decreased by 58%.